1. Field of the Invention
This invention relates generally to an offloading system by which hydrocarbon product is transferred from an offshore storage facility to a shuttle tanker. In particular, the offshore storage facility is a deepwater Floating Production Storage and Offloading vessel (FPSO) or a Tension Leg Platform or a SPAR Buoy where hydrocarbon product such as crude oil is temporarily stored after production from subsea wells.
2. Description of the Prior Art
In deep water operations, certain operational considerations make it desirable to offload hydrocarbons from a production and/or storage facility by running a pipeline to an offloading system, such as a CALM buoy, where a shuttle tanker may be moored and connected to a loading hose for filling its tanks with hydrocarbon products such as crude oil.
In a prior system described in U.S. Pat. No. 6,415,828 B1 (Duggal, et al), a product transfer system is disclosed in which a rigid or flexible pipeline from a FPSO or platform or the like extends in the sea above the sea bed for about a nautical mile where it terminates close to a CALM or SALM buoy, and where it is fluidly coupled to a flexible hose at a Flowline Termination Buoy (FTB) which is positioned by anchor legs below the wave kinematic zone. The other end of the flexible hose is fluidly coupled to a product swivel mounted on the single point mooring (SPM) buoy such as a CALM or a SALM. A shuttle tanker is moored to the SPM buoy by a hawser secured to a rotatable portion of the CALM buoy. A hose from a rotatable output of the product swivel connects to the shuttle tanker to complete the product flow path from the FPSO (or platform) to the shuttle tanker.
The prior system described above requires a SPM for shuttle tankers that do not have dynamic positioning systems on board and require mooring and fluid transfer from the SPM buoy. Nevertheless, certain tankers that do not need a mooring system to a SPM buoy, but nevertheless require connection to the pipeline which extends from the storage facility. Such connection should be at a submerged location below the wave kinematic zone as described in the above-mentioned U.S. Pat. No. 6,415,828.
3. Identification of Objects of the Invention
A primary object of the invention is to provide a submerged termination buoy (FTB) for coupling of an end of a pipeline from an offshore hydrocarbon storage facility to a marine hose for direct coupling with a shuttle tanker without the need for an intermediate SPM buoy.
Another object of this invention is to provide a transfer arrangement by which a fluid flowpath from an offshore storage facility to a shuttle tanker is provided with a pipeline marine hose connection at a Flowline Termination Buoy (FTB) kinematic zone and where the marine hose is connected to the shuttle tanker (especially, a dynamically positioned tanker) without the need for a SPM buoy.
The objects identified above along with other advantages and features are provided in a transfer arrangement including a Flowline Termination Buoy (FTB) moored to the sea floor that is used to support and/or terminate one or more flowlines near the ocean surface, but deep enough below the wave kinematic zone such that the flowlines are not subjected to damaging fatigue cycles. If multiple pipelines from the storage facility are required, multiple hoses which are fluidly coupled to the pipelines at the FTB may be fluidly coupled to a Hose Tee Buoy to a single floating hose string which can be fluidly coupled to the dynamically positioned shuttle tanker. A marker buoy is connected to the single floating hose string via a swivel, so that when the hose string is not connected to a tanker, the upper part of the hose string can weathervane according to sea conditions.